Enhanced microwave absorbing performance of Ni-containing SiCN ceramics by constructing multiple interfaces and in-situ generating MWCNTs

Abstract

Ni-containing SiCN ceramics as microwave absorbing materials were successfully synthesized by facile polymer derived ceramics (PDCs) route using nickel acetates tetrahydrate (Ni(Ac)2·4H2O) and polysilazane (PSZ) as raw materials and pyrolyzing at 1200 °C. After introducing Ni(Ac)2·4H2O, a large number of multi-walled carbon nanotubes (MWCNTs) were in-situ formed in Ni-containing SiCN ceramics. Besides, some crystalline phases, such as Si3N4, β-SiC, Ni2Si, Si2N2O and turbostratic carbon, were observed. The 3D conductive network constructed by the MWCNTs and multiple heterogeneous interfaces formed by various phases were generated in SiCN matrix, which enhanced the electromagnetic wave (EMW) absorbing performance of Ni-containing SiCN ceramics. The morphology and electromagnetic parameters of Ni-containing SiCN ceramics could be effectively regulated by changing the addition content of Ni(Ac)2·4H2O. The Ni-containing SiCN ceramics with the Ni(Ac)2·4H2O addition content of 15 wt% presented the best electromagnetic wave absorption property. Its minimum reflection loss (RLmin) reached −60.71 dB at 9.44 GHz with the thickness of 2.20 mm and effective absorption bandwidth (EAB) broadened to 4.36 GHz (13.64–18 GHz) at 1.38 mm. The excellent properties should be mainly attributed to the synergistic effects of good impendence matching, conduction loss and polarization relaxation loss.